The field of art to which this invention pertains is coating compositions which cure at ambient temperatures.
Coating compositions which cure under ambient temperature conditions have been known for a long time. The earliest of such coating compositions are coatings based on drying oils which cure by air oxidation. Other coating compositions which have been developed more recently are those based on the epoxide-carboxylic acid reaction, isocyanate-active-hydrogen reaction, polyaziridine-carboxylic acid reaction, and activated methylene-unsaturated acrylic reaction.
Film forming interpolymers of acrylic acid, acetoacetoxyethyl methacrylate, and monomers copolymerizable therewith are described in U.S. Pat. No. 3,554,987.
In U.S. Pat. No. No. 4,408,018, polymers containing pendant acetoacetate moieties are mixed with polyacrylates which contain more than one unsaturated acrylic group and are cured through Michael addition using a strong base as catalyst.
Crosslinking through Michael addition is also shown in European Patent Application No. 227,454. In this patent application, compounds containing a plurality of pendant acetoacetate groups are blended with compounds containing a plurality of ethylenically unsaturated acrylic groups and are cured with the addition of a strong base or an organometallic compound.
South Africa Patent No. 85-2044 describes coating compositions curable at ambient temperatures made from compositions which contain a plurality of activated methylene groups and ethylenically unsaturated carbonyl groups.
In an article by A. Noomen, entitled "Ambient Temperature Curable Coatings Based on Two Pack Binders", Organic Coatings Conference, Athens, Greece, June 1987, coating compositions which cure through the Michael addition reaction of acetoacetate-ketimine groups and acrylic-malonate groups are discussed.
Curable coating compositions based on the epoxide-carboxylic acid reaction are disclosed in U.S. Pat. Nos. 3,305,601 and 4,028,294 and European Patent Application No. 226,171.
U.S. Pat. No. 4,558,076 describes low temperature curable coating compositions made from carboxylic acid group containing polymers, polyepoxides and, as catalysts, aluminum, titanium or zirconium alkoxides or complexes thereof with a chelating agent.
In a presentation made at the Water-Borne & Higher-Solids Coatings Symposium in New Orleans, LA. on Feb. 3-5, 1988 by Robert J. Clemens entitled "A Comparison of Catalysts for Crosslinking Acetoacetylated Resins via the Michael Reaction", coatings curable at ambient temperatures are described. These coatings are made from acetoacetylated resins, polyacrylates and strong base catalysts, and care through Michael addition.
In U.S. Pat. No. 4,906,684, ambient caring coating compositions are made from aqueous dispersions of copolymers containing acetoacetoxy groups, glycidyl groups and carboxylic acid groups.
U.S. Pat. No. 4,987,177 describes coating compositions which cure at ambient temperatures and which are made from (A) a copolymer of acrylic and vinyl monomers having pending from the polymer an amino group, and (B) an acrylic crosslinking monomer containing pendant glycidyl groups and acetoacetate groups.
There is a continuing need for ambient temperature curing coating compositions which have low volatile organic solvent content (VOC), lengthy pot life, and fast coating performance development upon application to a substrate.